Release password store synchronously on UI thread when shtudown starts.


BUG=274705
NOTRY=true

Review URL: https://chromiumcodereview.appspot.com/24210004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@224525 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 224525